Is there a way to check and ensure the primary cooling fan wire has the correct continuity coming from my aftermarket engine harness. I have a custom made extended Speartech harness for my 2004 tahoe 5.3l swap into my 1936 chevy coupe. I am using aftermarket gauges that are working great. I just started the motor about 10 days ago and am having problems with the radiator fan coming on. I am using an aftermarket chassis/body wiring warness from a very well known company that so far works great. Now, for whatever reason I cannot get my 16" electric cooling fan to come on.
Here is current info:
1. Running 2 temp sensors , A) installed a passenger side sensor on block for use on my aftermarket temp gauge only., works great B) using the factory driver side sensor for my custom Speartech harness to trigger the fan controlled relay to ground
2. For cooling I am using a single 16" Maradyne fan that came with a relay and wiring harness that can accomodate 2 fans.
3. My relay wiring is as follows... RELAY TERMINAL #30, to hot constant 12 volt directly to battery with an inline 30A fuse. RELAY TERMINAL #85 from ignition side (labeled in aftermarket harness and tested perfect with "key on", RELAY TERMINAL #87 to cooling fan wiring positve side, and last RELAY TERMINAL #86 from PCM using the Speattech dark green labeled Primary Cooling Fan Wire
4. All sensors, wiring and relays are brand new. PCM was flashed for this build with coolant fan set at 165 degrees.

So why isn't fan coming on, even when temps get to 210 degrees? I can ground the relay prior to terminal 86 manually and the fan will operate for about 15 seconds then shuts off (even though temps are at or above 200 degrees). So I'm guessing either the Speartech wire for sensor ground signal has a break or the PCM was not configured appropriatley. Is there a way to test the PCM signal wire for continuity?Maybe I am missing something, any advise would be appreciated

 

Pull the wire out of the pcm connector and ground it. Fan should turn on.

 

For those that run into this problem, make sure you stress and verify your ECU aftermarket programmer sets this to YOUR specifications. I finally figured out the programmer never set the ECU to 165 for electric fan engaugement. I am a very old school chevy builder and was used to 165-180 manual thermo's with clutch fans. All is good now. I just wanted other builders going into the LS market to understand that LS based motors do not engauge fans until 210 (this was tough for me to get used to). As I live in Texas I wanted to try and keep this as cool as possible for my Vintage Air AC